#app {
  background: palegoldenrod;
}

#tupian {
  background-image: url(../images/a.png);
  width: 466px;
  height: 453px;
}

#webkit {
  width: 466px;
  height: 453px;
  background: paleturquoise;
  transform: rotate(45deg);
}

#wuxiao {
  width: 466px;
  height: 453px;
  background: forestgreen;
}